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#include <QtWidgets>

#include "dragwidget.h"


//! [0]
DragWidget::DragWidget(QWidget *parent)
    : QFrame(parent)
{
    setMinimumSize(200, 200);
    resize(500,500);

    //这行代码的作用是设置QFrame窗口部件的框架样式为一个凹陷的、有样式化面板的外观。
    //这样，QFrame窗口部件将具有一个凹陷的边框和一个与众不同的面板，
    //以改善其在用户界面中的可视性和交互性。
    setFrameStyle(QFrame::Sunken | QFrame::StyledPanel);

    //允许拖拽事件
    setAcceptDrops(true);

    QLabel *boatIcon = new QLabel(this);
    boatIcon->setPixmap(QPixmap(":/images/boat.png"));
    boatIcon->move(10, 10);

    /***
    这行代码显示boatIcon。默认情况下
    新创建的控件是不可见的，需要调用show()方法来使其可见。
    这行代码设置boatIcon的属性，使其在关闭时自动删除。
    Qt::WA_DeleteOnClose是一个属性，
    当控件关闭时，它会自动释放其占用的内存。这有助于避免内存泄漏。
    ***/
    boatIcon->setAttribute(Qt::WA_DeleteOnClose);
    boatIcon->show();

}
//! [0]

void DragWidget::dragEnterEvent(QDragEnterEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-ycn")) {
        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

void DragWidget::dragMoveEvent(QDragMoveEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-ycn")) {
        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

void DragWidget::dropEvent(QDropEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-ycn")) {
        QByteArray itemData = event->mimeData()->data("application/x-ycn");
        QDataStream dataStream(&itemData, QIODevice::ReadOnly);

        QPixmap pixmap;
        QPoint offset;
        dataStream >> pixmap >> offset;

        QLabel *newIcon = new QLabel(this);
        newIcon->setPixmap(pixmap);
        newIcon->move(event->pos() - offset);
        newIcon->show();
        newIcon->setAttribute(Qt::WA_DeleteOnClose);

        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

//! [1]
void DragWidget::mousePressEvent(QMouseEvent *event)
{
    QLabel *child = static_cast<QLabel*>(childAt(event->pos()));
    if (!child)
        return;

    QPixmap pixmap = *child->pixmap();

    QByteArray itemData;
    QDataStream dataStream(&itemData, QIODevice::WriteOnly);
    dataStream << pixmap << QPoint(event->pos() - child->pos());
//! [1]

//! [2]
    QMimeData *mimeData = new QMimeData;
    mimeData->setData("application/x-ycn", itemData);
//! [2]

//! [3]
    QDrag *drag = new QDrag(this);
    drag->setMimeData(mimeData);
    drag->setPixmap(pixmap);
    drag->setHotSpot(event->pos() - child->pos());

//! [3]

    QPixmap tempPixmap = pixmap;
    QPainter painter;
    painter.begin(&tempPixmap);
    painter.fillRect(pixmap.rect(), QColor(255, 127, 127,127));
    painter.end();

    child->setPixmap(tempPixmap);

    //启动拖拽事件，
    if (drag->exec(Qt::CopyAction | Qt::MoveAction, Qt::CopyAction) == Qt::MoveAction) {
        //如果是在本窗口，则视为移动
        child->close();
    } else {
         //如果是在其他窗口，则视为复制
        child->show();
        child->setPixmap(pixmap);
    }
}
